Sam allowed John

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Sam allowed John

by sanju09 » Tue Mar 17, 2009 3:09 am
In a 100m race, Sam beats John by 4 seconds. On the contrary, if Sam allowed John to start 16m ahead of Sam, then Sam and John reach the finishing point at the same time. How long does Sam take to run the 100m race?

A. 4 seconds

B. 25 seconds

C. 29 seconds

D. 21 seconds

E. 6.25 seconds

OA D
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by lav » Tue Mar 17, 2009 5:05 am
man this was tricky ....

assume sam ran at speed 's' both the times
and john ran at speed 'j' both the times
and we know distance is 100m

Now ..

(100/j)-(100/s) = 4

and 84/j=100/s
solving 2nd will give s=(25/21)j
substitute in 1st get j=4
hence s = (25x4)/21

ans is 100/s substitute and get ans = 21
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